Why Do Stars Shine and the Science of Light
Stars are giant balls of plasma (an ionized gas consisting of positive ions and free electrons) held together by their own force of gravity. The stars are ever crushing in on themselves because of gravitational pull. The friction caused by that force creates heat. Because the interior heat of the star gets so hot (up to 15 million kelvin!) it causes a nuclear fusion. The fusion happens between atoms of hydrogen and helium and this reaction causes a huge amount of energy in the form of gamma rays. The gamma rays are trapped inside the center of the star (where they are formed) and push outward, this is why the star does not collapse in on itself. The gamma ray can live within a star for an infinite amount of time, in a cycle of being absorbed and dislodged over and over again until it reaches the surface. Through the gamma ray journey to the surface of the star it loses energy and becomes a visible light photon. The light photon ejects the surface of the star and heads out in a straight line through space, it can go on for an infinite amount of time until it runs into an object.
What happens to a photon after it hits your eye? The photon is absorbed in the eye and converted into a chemical reaction. They stimulate the cones and rods of your retina which in turn produce a chemical response (rods - rhodosin photopigment, cones – photopsins). The cones are sensitive to color and the rods are sensitive to light. The chemical reaction causes an electrical signal from the optic nerve to the brain and enables us to “see”
Strobes: also known as arc lamps. Electricity attached to two tungsten electrodes (tungsten is extremely combustible but has a high melting point) heats up the xenon gas inside the flash tube, and splits the gas atoms through ionization. The atoms (positively charged ions and negatively charged electrons) speed off in opposite directions bumping up against each other. That friction creates heat which produces a photon and light!
Law of refraction – when light passes from one transparent medium to another it bends the light, the incident angle depends on how much the material slows down the light.
Law of reflection – when light hits a smooth surface and bounces off "the angle of incidence equals the angle of reflection" meaning whatever angle the light hits a reflective surface is going to equal the same angle it bounces off.
Scattering – when light hits a rough, uneven surface and bounces in many directions.
Photons are unique in that they are both a wavelength and a particle, the energy wave is built of red, green, and blue in the visible spectrum.
Quantum Physics is the nature and behavior of matter and energy on the atomic and subatomic level (like splitting atoms and creating photons).
We get noise in our digital images because photons move in flux and in variable quantities. They do not move uniformly therefore they do not all hit the sensor at the same time. The dark area lacking light then transmits electronic circuit noise from the sensor producing random colored pixels.
Noise in film is determined by the grain size. The grain is the light sensitive silver halide that is layered on the film. The higher ISO film the larger the grain size.
80% percent of the world supply of tungsten is controlled by China.
Gas discharge lamps: is an electric light using a gas-filled tube; these include fluorescent lamps, metal-halide lamps, sodium-vapor lamps and neon lights.
Florescent lamps are tubes that contain gas, a mercury vapor, where electricity is passed through the gas and activates it to create an ultra violet light (not visible to the naked eye). Each tube has a phosphor coating on the inside, as the light passes through it becomes visible to the naked eye.
Modeling bulbs are incandescent lamps where electricity moves through a thin piece of filament (wire) that heats up and burns bright.